Nickel phenolate stabilized polypropylene



2,971,940 Patented Feb. 14, 1961 United States PatefitfOfiice 2,971,940 NICKEL PHENOLATE STABILIZED POLYPROPYLENE Charles H. Fuchsman, Cleveland Heights, Albrigh't M. Nicholson, Warrensville Heights, and Stanley B. Elliott, Bedford, Ohio, assignors to Ferro Corporation, Cleveland, Ohio, acorporation of Ohio No Drawing. Filed Mar. 20, 1959, Ser. No. 800,629 8 Claims. (Cl. 260,45.75)

This invention relates to stabilized crystalline polypropylene compositions, andvmore particularly to crystalline polypropylenes which have been stabilized with nickel phenolates hereinafter more particularly described.

The inertness of crystalline polypropylenes under a variety of conditions has resulted in increasingly Widespread use in diverse fields of application. One of the factors which limits present usefulness in outdoor applications is the tendency to deteriorate under the influence of the ultraviolet light present in sunlight. This deterioration is detectable in a number of ways, chief of which is an increase in brittleness and a decrease in elongation under tensile stress. These changes in the original characteristics of the polypropylene cause sheets'or fibers of such materials when exposed to weather to break and tear readily. Utilization of these materials in sheet or fiber form, in covering greenhouses, draping open areas in building construction, etc. is consequently much reduced.

Attempts have been made to use various additives for the prevention of ultraviolet light deterioration'of crystal line polypropylenes. alone or with antioxidants reduces light deterioration. However, the resulting product is opaque to visible light and thus of limited utility. Other attempts to meet this problem have included admixture of various commercially available ultraviolet absorbers with the polypropylene. Some substituted benzophenones which are excellent ultraviolet light absorbers are very difiicult to retain in admixture with polypropylene. These materials have, however, conferred insutficient light stability, or have proved largely incompatible with polypropylenes,. and have migrated to the surface of the plastics where they are readily removed by rain and wind-borne abrasive dusts. Any unremoved efllorescence is unsightly and opaque.

It is a principal object of this invention, therefore, to provide improved crystalline polypropylene compositions better. able to withstand the deleterious effects of prolonged exposure to ultraviolet light sources. L.

Other objects of this invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the appended claims, the following description setting forth in detail certain illustrative embodiments of the invention, such disclosed means constituting, however, but a few of the various forms in which the principle of this invention may be employed. 3 I

It has been found that certain bis-(p alkylphen'ol) monosulphides, in which part or all of the ability (elongation) in useful degrees. In the absence of Thus, the addition of carbon black phenolic hydrog'enatoms have been replaced-by nickel possess important light stabilization characteristics when used as additives in crystalline polypropylenes, Broadly stated, therefore, this invention comprises crystalline polypro; pylene containing in intimate admixture about 0.05% to about 5% by weight of a nickel phenolate of. o,o'-bis-(p-alkylphenol) monosulphide in which. the alkyl group contains from 2 to 12 carbon atoms.

The term stabilized and the various forms of the word used hereinhas reference to improvementrin the therewith from the stabilizers of this invention, crystalline polypropylenes, upon exposure to ultraviolet light, such as present in sunlight, rapidly become brittle and sheets thereof break or tear readily.

The term phenolate as used herein is used in the generic sense, i.e., as identifying a compound characterized by the presence therein of the MOQgroup where M is the hydrogen equivalent of nickel and Q is an aromatic ring, a carbon atom of which is linked to the metal through the oxygen atom. The term phenolphenolate, not in common usage, will be understood as a phenolate compound containing more than one phenolic group, in which some, but not all of the phenolic hydrogens have been replaced by nickel. Full phenolate as used herein refers to a phenolate compound derived from a phenolic compound containing more than one phenolic group in which all the phenolic hydrogen atoms have been replaced by the hydrogen equivalent of nickel.

The class of polypropylenes to which the present invention is primarily directed and in which stabilization against the deleterious eifects of ultraviolet light exposure is achieved, is characterized as follows: The contemplated polymers have crystalline structure as determined by X-ray analysis; a number average molecular weight range of from about 45,000 to 100,000 and higher; a melting point in the range of from about 140. C. to about 170 C. when measured by a birefringence method, reduced specific viscosities (RSV) of about 1 to about 9, and densities of 0.87 to 0.93. By the term reduced viscosity is meant the 1 sp./c. determined on a solution of 0.1 g. of the polymer in g. of decalin at C.

Crystalline polypropylenes having the foregoing characteristics may be prepared by any of the well-known processes of polymerizing propylene to a crystalline or isotactic polymer, as for example by the processes described in Belgian Patents 530,617; 538,782; 543,259; 546,846, etc.

By one such method, crystalline polypropylenes having the foregoing characteristics are separated from a liquid phase bulk polymerization reaction mass. In general, polymerization is effected in the presence of certain metalcontaining catalysts where the metal is of the 4th or 6th group of the periodic system. The reaction pressure ranges from atmospheric to as high as 30 atmospheres, and the temperature ranges between 20 C. and C. Solvent or diluent may be present, or the liquid monomer may be the only material present in addition to the catalyst. The reaction is conducted in the absence of oxygen and water. Various fractions of polymerized mass are separated by special sequential solvent treatment. For complete details, reference may be had to the patent of Natta and Ziegler, Belgian Patent 538,782 for the preparation of crystalline polypropylene compositions in which stabilization against degradation by ultraviolet light is secured in accordance herewith. Other methods of producing crystalline polypropylenes may, of course, be employed. The polymers in the commercial form usually have other ingredients present in small amounts, e.g. heat stabilizers, and antioxidants.

Crystalline polypropylenes, are unique among polyolefins in possessing physical and chemical properties and behavior characteristics not common to other crystalline polyalkylenes. For example, it is a general rule that as the carbon content of the monomer from which the crystalline polymer is made increases, the temperature of transition from the crystalline to the amorphous state decreases. However, the transition temperature for crystalline polypropylene is higherthan that for crystalline polyethylene or crystalline polybutylene H r; In further distinction from substantially nnbranched polyalkylenes every othercarbon atom in the main carbon chain of this crystalline polypropylene polymer is tertiary. Such carbon atoms are paiticularlysusceptible to attack by ultraviolet light and by oxygen. Thus crystalline polypropylene is qnalitatiyely distinguishable in susceptibility to deterioration from other polyalkylenes notv characterized by a high proportion of tertiary carbon atoms. g I Inclusion of additives in highly crystalline "polymeric materials poses pmuenig nmag among which is the tendency of many additivesto exude to the turface of the polymer. .Certain substituted benzophenones I which are 'encellentultravioletlight absorbers are very diflicult to retain in admixture with highly crystalline polypropylene. A primary advantage of the'nickel phenolates of the presentrinvention,ywhether the full phenolate or'a nickel lphenol-phcnola'te is theirabilit'y to'con'fer 'stabili iat'ion and remain in compatible relationship with the crystalline polypropylene and other additives, e.g. antioxidants land/or heat stabilizers normally incorporated in minor amounts,je.'g. lefssfthan 1% 'by weight, in commercially available crystallinefpolypropylene's. I i v Another of'the 'piimaryjadvantages of the nickel'ph- "nolates ofrthefpresflent invention and. especially nickel phenolates derived "from crystalline 'o,o-bis (p-'alkylphen01) monosulphides, e.g." cry alli'ne 'o,o"-'bisQ-(pl',1, 3 .13- tetrametliylbutylphenol) monosulphide, "is that in the minor amounts efiective to stabilize crystalline jp'olypropylene compositions hecoloration imparted to the-plasticefby the add itixz e;iisjnot objectionable. Effective sta- -bilization without: substantial coloration has 'beenfloiig sought for-polypropylene compositions, Thus; inapplications, such as, the covering of greenhouses and structural openings, the normal light transmission'of the plastic material is not' greatly "altered by the'inclusion' of the nickel phenolate s hereof. i v

The improved stabilized compositions of the presentinve'ntion are best 'inade'irom a crystalline polypropylene composition to whichfhas been added by conventional procedures, anickel phenolate prepared frorn'a crys't' fne 'o,o'-bis-(p alkylphenol) monosulpbide. Oi "particuljar utility in this respect are nickel phenol-phenolates 'andjfull phenolates derived "from crystalline -o;o'-bis-(p"-'l,l,'3,3- tetram'ethylbutylphenol) monosulphide. FThe nickel d erivativ'es thereof are" fullyi lescribed in the followingieitamples and alsoin the applicationbi Nicholson "and Zaremsky, Serial No 789,908,"filed January 9, '19 59,"to which reference may he had. w

Briefly, the nickel-phenol-phenolates may be obtained by a metathetic reaction between thesodium phenol-plienolates of the bis-(p alkylphen'ol) monosulphideanda nickel halide'in ananhydrous medium and have the probable structure of Formula I.

4 Formula I Ltierntiaaane nickel henel phenolats inay'beobtained by direct reaction of-a hydrated nickel salt of a. weak acid, e.g. hydrated nickel acetate to yield a product 5 having theprobable structure of Formula II.

R Formula ll v In the-above Formulae I and n, R is ana1kyl'gronpiof from'2 to 12 carbon 'atoms. The dotted lines of the forego'm formulae "represent interatomic linkages or the lchelate type andsimple hydrogen bonding in the case'of f'the free phenolic group. Thelines hearing I arrows reprejsent interchangeable linkages which isuggest the "equiy- 3O falence "of t'wo 'bis; (p-alkylphenol) 'm'o'nosulphide units "in theirreltionshipjto thenickel'atom. H I I. v

j phenolatesofthe present" invention arep'rodncedbys 'nsi'ng"cbrrespondinglyincreased 'amounts'fofreactants'to yieldproductsofthe"general for- "mula HFbelow:

v Formula III .A method 'of preparinga phenol monosulphide of-good "qualityiisillustrated in the preparation of one crystalline -o;o' bis*(pe'octylphenol) monosulphide. -By'other pro- ;cedures well known in'the'art (see Mikeska etal. 2,139,- 321), o,o'-his-(p-tert.-butylphenol) monosulphide, 0,0- bis ,-(p,-tert.-amylphenol) monosulphide, o;o'=bis-(p-2- ethylhe tylphenol) monosulphide, o,o bis-(-p-nonylphenol) monosuiphide, o;o'-bis -(p-laurylphenol) monosulphide may also ,be-prepa'red, as well as any of the other ogo bis-(p-alkylphenol)' monosulphides in which the alkyl group contains from 2 to 12 carbon atoms; in branched o r linearrelationship,usefulherein may be prepared. Yarious;polymericiby-products are often formed simultaneously withthe desired bis-(p-alkylphenol)monosul- Phi Si ;e he m ke der e. q r'p m r i teriai tends to, be objectionably dark even at 7 dis- .P qnt cffiz tqmsb i s u u l y ne e y t eflect a separation betyyeenthe by-product polymer sulphide and the bis-(p-alkylphenol).monosulphide prior to fillsn dvs a. tet r li sa T i s n sti n sm -'.;p .hs wi r namsa utss fease u i iw tx d n in; b new: e alky f bs i o 911 i i E 9 ez m ls sn ow llus mtesnhs' c el S a a H il fl ilzb t w fiej h 6 0 r s) a s aj di t: ra mi t perature and then 'cooledto'45 Fiwitlr strong' agitation.

' m marches-ramsthe p lin ?!-teti'ainethylbutylpliencl 1 grains of petroleum ether (B.P. 30-60 6.). I.highly sulphurized product is soluble in the petroleum ether.

of an o,o'-bis-(p-octylphenol) monosulphide.

sulphide.

to remove all the xylene. cooled by any of several procedures to yield the solid '-tends to" come out of solution, but'this is of little, concern as longv as the mixture is kept under agitation. SOg-rams of Sci; admixed and in solution with '50 grams of CC Lare added over a period of about 1 hour, and the mixture allowed to agitate for an hour after the addition has ceased. After overnight.standing,-the mixture is washed with water to extract HCl, cooled and diluted with 200 The more However, the o,o'-bis-(p-1,1,3;3-tetramethylbutylphenol) monosulphide separates out as a crystalline white solid which is easily filtered. This is an example Alternatively, high vacuum distillation may be employed to separate out desired bis-(p-alkylphenol) monosulphides from reaction masses.

' As indicated above, the nickel salts may be prepared .;by two basically difierent methods; metathesis and direct ,reaction. r j,

EXAMPLE 2 The nickel-phenolate, that is, the fully substituted bis- (p-alkylphenol) monosulphide illustrated in Formula III 'above was prepared as follows: i

o,o'-Bis-(p-l,l,3,3 tetramethylbutylphenol) monosulphide obtained from the above reaction was converted into the full sodium phenolate by reaction at room temperature with a stoichiometric amount of sodium ethoxide in absolute ethanol solution) followed by reaction quantity of NiCl in absolute al- Sodium chloride is precipitated and filtered off.

' EXAMPLE 3" To produce the nickel phenol-phenolate, a procedure identical with that given in Example 2 except that only one-half of the stoichiometric amount of sodium ethoxide required to react with all the phenolic hydroxyl was used. The amount of nickel chloride added was then stoichiometrically equivalent to the reduced amount of :sodium. The final product in this case was a light green crystalline product corresponding essentially tothe for- .mula of the type given in Formula I. This product had a nickel content of 5.5% found as against a theoretical percentage of 6.2%. The deficiency in nickel was attributed to the presence of unreacted bis-(octylphenol) EXAMPLE 4 To produce the nickel phenol-phenolate particularly useful in accordance with this invention, a quantity of nickel acetate tetrahydrate dissolved in xylene (1:1) and equivalent to half the number of phenolic OH groups in the sulphurized phenol is heated with a 40% solution of o,o'- bis-(p-1,1,3,3-tetramethylbutylphenol) monosulphide in xylene at or slightly below the boiling point of acetic acid. With continued heating the latter is distilled oif almost quantitatively. The xylene solution is filtered to .remove any xylene-insoluble impurities which may have formed during the reaction. The filtrate is evaporated The residual liquid may be product. The product is hard and friable and contains Ni (theoretical 6.1% Ni).

" EXAMPLE 5 A solution of p-tert-amylphenol (125 grams, melting point 94.595.0 C.) in ethylene dichloride (630 grams) was heated to boiling under reflux and a solution of sul- ,fl1.i' dichloride (40 l'grams) .was added chloride 'gas evolved during the reaction was remov.e;1

grams) in ethylene dichloride (120 slowly, with agitation, the hydrogen and benzene washings were combined and distilled and the following fractions were taken:

Forerun To 181 01/0/13 1.30 g. Fraction 1 181-482 C./0/13 mm., 1.62 g. Fraction-2 182 C./0/13 mm., 1.48 g. Fraction3 181185 C./0/13 Inn-1., 2.64 g'.

On standing overnight fractions 1,2 and 3 crystallized.

.The crystals were separated and recrystallized twicefrom hexane. Fractions 1 and 3 combined yielded 2.76 grams .of bis-(p-tert-amylphenol) monosulfide having a melting point of 99.5-100.5 C. Two recrystallizations of fraction 2 yielded 1.10 grams of bis-(p-tert-amylphenol) .monosulfide having a melting point of 100.010l.0 C. The analytical results on this product were: theoretical, carbon 73.70, hydrogen 8.44; found, carbon 73.75; hydrogen 8.53. To a solution of sodium (0.46 gram) in anhydrous ethanol (50 grams) was added 3.58 grams of the above bis-(p-tert-amylphenol) monosulfide. After the solution was complete, a solution of nickel chloride hexahydrate (2.38 grams) in anhydrous ethanol (50 grams) was add- .ed. The reaction mixture was stirred 15 minutes, hexane grams) was added, and the reaction mixture was then heated under reflux for 45 minutes. The sodium chlorid'e'that had formed was removed by filtration-and .washed with a small amount of benzene. The filtrate the diluents were removed by distillation. The residue was dissolved in hexane and the solution filtered, after which 95% ethanol was added to the filtrate and the hexane was removed by distillation. On cooling to room temperature the nickel phenol-phenolate of the o,o'-bis-(p-tert-arnylphenol) monosulfide crystallized in the form of green crystals. This crystalline product was separated and dried at 20 C. in vacuo for 16 hours. It did not melt below 360 C. The analytical results on this product were: theoretical, nickel 14.1%, carbon 63.6%, hydrogen 6.8%; found, nickel (by direct ash) 16.9%, carbon 57.45%, hydrogen 6.86%.

EXAMPLE 6 A commercial sample of crystalline polypropylene was mixed with a carefully prepared sample of the nickel phenolphenolate of o,o-bis-(p-1,l,3,3-tetramethylbutylphenol) monosulphide produced in accordance with Example 4 above. The nickel compound constituted 0.5% of the mixture. The mixture was pressed at 450 F. for 15 minutes to yield a clear very light green sheet. Samples of this sheet, together with control sheets contain- .ing no additive were then exposed to intense ultraviolet light. Every 24 hours the samples were tested by bending sharply through 180. Cracking along the bend was regarded as failure. The control samples failed between 72 and 96 hours. The samplescontaining the additive had not failed after 390 hours. 1 f

The nickel phenol-phenolate of o,o'-bis-(p1,l,3,3- tetramethylbutylphenol) monosulphide produced in ac" oordance withthe procedure of Example 4 above was solvent slurry blended with commercial samples of crystalline polypropylene having a density of 0.90 and-a crystalline melting point of l67.2 C. (birefringence) and a specific viscosity of 0.127. Plaques of both stabilized and control (nickel phenol-phenolate free) sample 5 min. thick were pressed under 2000 p.s.i. pressure at 215' C. for 15.minutes and tested by exposure to ultraviolet light in a Fadc-Ometer. The results in Table I-were; note fcrysialliii' polypiopy 'eiie.

ewe-13040 17 for indicated concentrations n -crystalline polypropylene samples.

' 'samples A, B and Gare dltl'erent lots ot commercial polypropylene.

The nickel phenol pli'en phenol) monosulflde prepared in Example 5 {solvent slurry blended'with a crystalline pew ropmefiemavi g an RSV e43, Plaques at the so-stg bnizeg'pel prepyn one and a controlcon'taini'ng'n'o stabilizers mm. thick were pressed under 200'p.s.i.'pressureat 215 minutes and tested by exposure to ultraviolet light-inn "Fade-Ometer. Thecontrol containing nostabilizer'failed in less than 24 hours The' polypropylene plaquepontaining 05 "of the nickel phenol-'phenolate et; o',o'-'bisand had not failed after 168 hours.

Another procedure "for incorporating thefl st'abilizers is follows: finely divided' stabilizer isfintensively mixed with fine polypropylene powder, tli'e n'extrudd'i'lltb 'molding powder.

ln like manner crystalline ply repyl iieepmpesir efis "containing otherfnickel 'pherjiolates, fei'therfull nickel phenolates, or nickel "phenol phnolates, or the jo',o' bis- (p-alk'ylphenon "monoisulphides f inaye be prepared. I, In general the stabilizers of 'the'pres'ent 'invention afe 'etfectiveover "a much broadenra'ng'e of'cjoncentra'tion, namely, 0.0 5% to about 57 The'lowerliniit of this ran e, is a threshold limit. Coloration 'impar'ted tothe polypropylene by'the stabilizers hereof is "negligible 1: at concentrations which are optimum, feig. Olt'o While there appears to be continued improvement in ultraviolet stabilization ateencentratiens' above 1 ,i that isQiip to 5% by weight and intermediate" quantities,' a fter amounts of about 1% by weight have been addedto the crystalline polypropylene -compositions, the amount of improvement in flexibility and elongation after hours exposure'to intense ultravioletlight'doesnot appear'to'justify the addedcost of the's'tab'ili'zr. Mere- "ever, coloration isincreas'edfat the highrf'coiice'fitrations above 1% 'althoug'histill within acceptable raagesfier ma pu p ses. 7

It has been found that'variations in the"'struc'ture, car- 'bon content and location of the alkyl"substitunts i s"pr- 'r ifi ssible "Without destroying the "desirable characteristics of th'e phenol-'phenolate or]pl'ieiiol'ajte"p'rc'it'iiiiijt. were cannot lief aj'steri'cally' hinderingflsubstituent in the oi'flio position of the phnol which 'is eife'ctive topr'evem nietal'substitution. Thus, in additionto the varieusfun phenolat es and phenol-phenolates above' rrienti'ond, the nickel phenol-phenolates of 'lo',o"-bis-( p t' v phenoh monosulphide, "the nickel"phenol'-phenolate of "o,o 'bis-(p-ethylphenol) monosulphide, the nickel phenolphenolate of o,of-"bis tp2ethylhexyl phenol) monosulphidqthefnickel phenol? I 'en'olate'-- OfopT-bis-IpJErtiaifiy :Tbutylphenol) no'sulp'hide, the fullf nic'kelphenolate of o;o"-fl" is-(p-fethylp'ihenol) 'm'o'n'os'ulphidmf the "full new *phen'olate of o,o'-bis'-'( tert. ylphenon "monosu'lphide, fullnickel fphen'olate "of d,Q'-bis'- (nonylphenol monlphide, the fullniclt'el "phenolate orop i eiwaoylphenolfmonosulp idgjare useful as stabil for The nen i andneae'eyr raups branched groups whose basic 'structure maybe oon 'ceived of as derived from the trimerization of propylene and isosutylene respectively. Small quantities of' ortho -a'1ky1substituted rings and-"ortho-para dialkyl substituted rings'ai'e often found as impurities in the para substituted phenols from which the monosulph-ides areproii'uce'd. The presence ofsuch impurities has not been fou'nd to have any efiect on the eflicacy ofthe nickel 'phenblates, whe ther full or partial, ultimately -obtained therefrom. Likewise,-presence of meta alkyl substitu- 'tion in the para-alkyl phenol nucleus maybe tolerated.

There has thus been provided "a stabilized crystalline polypropylene coifiposition w 'ch-is by virtue of the incl usion of from'-0.05% to-'about'5% 2by we'i'ghtof-the'sta- 'bilizer of. the present invention to withstand exposure 'to the deleterious efiects of'u1traviolet-light for prolonged without 1 becoming unduly brittle 'afid inflexible. further -adva'nt-age 6f these--'compositions is that the degree of coloration added to the polymer by the amounts of the stabilizers indicatd-iss1ieh as to preserve much of 'the translucency and lightcolor of the polymer. Oi -course,other-ingredients may be added 'to the compositions of the present invention such as, forexample, antioxidants of-the type used for heat stabilization, pigments, plasticizers, -'-fillers, additional stabilizers against light, etc., without substantially alteringthemanner in which-the compositionsof this invention operate. Crystalline polypropylene compositions stabilized in accordanceherewith are useful in the -form of extruded films or fibersgand-cast or molded 'arti cles, While-we are-not certain of the-phenomenon occurring by virtueof the inclusion oi the metal "compounds of the present-invention, it =is;believed that embrittlement and; loss of flexibility in the untreated vpolyalkylenes are theresult cif cross-linking and increase in molecular weight ;of the polymer under the influence of ultraviolet light, whether from an artificial or a naturalsource. The metal phenolattes ofthe present-invention appear to havethe' ability tmprevent cross-linkage in thepolymer.

oth'ermodes of applying'the principle of invention may-"be employed instead of those-specifically set 'forth above, changes being made as regardsthe details -herein disclosed, provided the elements T fset forth in -any ofthe following claims, orthe-equivalentof such,=be employed.

-=It'is' theretore, particularly pointed out 'and distinctly claimed-as the invention:

1."A crystalline vpolypropylne composition containing in l intimate atlmixture therewith from about 0.05% to about 5% by weight of a nickel phenolate of 'abis- (p-alkylphenol) monosulphide in which the alkyl group contains from 2 to 12carbon'at'oms, and which coaots ';in 5 said *crysta-lline polypropylene to preserve elongation "and flexibility therein after exposure toultraviolet light.

2; A c'rystalline polypropylene composition eontaining in-intimate admixture therewith from about 0.05% to about- 5% by weightof a iull nickel-phenolate-of a :bis- (p -alkylphenol) Q monosulphide in whichthe -alkyl 'groilp eontains from '2'to -l2-carbon atomsfafid which coaots in said crystallinepolypropylene to preserve elongation and-flexibility thereinafter exposure to ultr'a'violet light.

3. A 'crystalline {polypropylene cdmposititm containin'g-in -intimate admixture therewith fiom" about 0. )5% to about 5% 1 by i weight of a nickel phenol-phenolaite 0f a bis-(p-a'lky-lphenol) -rrionosulphlde in which the 1 alkyl 'group oontain's -f1"orn"2"to-12 ca bon' a'toms, and whiclt coacts in said crystalline polypropylene *to preserye elongation and flexibility therein after exposure to ultra violet light.

A crystalline polypropylene compositionfjcontaining 'in intimate admixture therewithfrom about"0.Q5'%"to "about 5% by weight 'of""the"'inickel'"phenol phe claw-at aidfcrystallinefpdlypropylne"to :pieserv elongation 5. A crystalline polypropylene composition containing in intimate admixture therewith from about 0.05% to about 5% by weight of the nickel phenol-phenolate of o,o'-bis-(p-nonylphenol) monosulphide, and which coacts in said crystalline polypropylene to preserve elongation and flexibility therein after exposure to ultraviolet light.

6. A light colored crystalline polypropylene composition containing in intimate admixture therewith from about 0.1% to about 1% by weight of the nickel phenolphenolate of o,o-bis-(p 1,l,3,3 tetramethylbutylphenol) monosulphide, and which coacts in said crystalline polypropylene to preserve elongation and flexibility therein after exposure to ultraviolet light.

7. The method of preserving the elongation and flexibility of a crystalline polypropylene composition after prolonged exposure to ultraviolet light which comprises intimately admixing therewith from about 0.05% to about 5% by weight of a nickel phenolate of a bis-(p- References Cited in the file of this patent UNITED STATES PATENTS 2,340,938 Daly Feb. 8, 1944 

1. A CRYSTALLINE POLYPROPYLENE COMPOSITION CONTAINING IN INTIMATE ADMIXTURE THEREWITH FROM ABOUT 0.05% TO ABOUT 5% BY WEIGHT OF A NICKEL PHENOLATE OF A BIS(P-ALKYLPHENOL) MONOSULPHIDE IN WHICH THE ALKYL GROUP CONTAINS FROM 2 TO 12 CARBON ATOMS, AND WHICH COACTS IN SAID CRYSTALLINE POLYPROPYLENE TO PRESERVE ELONGATION AND FLEXIBILITY THEREIN AFTER EXPOSURE TO ULTRAVIOLET LIGHT. 